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PubMed2005

A hierarchical Bayesian birth cohort analysis from incomplete registry data: evaluating the trends in the age of onset of insulin-dependent diabetes mellitus (T1DM).

Childhood diabetes is one of the major non-communicable diseases in children under 15 years of age. It requires a life-long insulin treatment and may lead to serious complications. Along with the worldwide increase in the incidence several countries have recently reported a decreasing trend in the age of onset of the disease. The aim of this study is to analyse long-term data on the incidence of the childhood diabetes in Finland from the birth cohorts perspective. The annual incidence data were available for the period 1965--1996 which translates into 1951--1996 birth cohorts. Hence the data consist of completely and partially observed cohorts. Bayesian modelling was employed in the analysis. Several different priors and cohort combinations were tried in order to determine the sensitivity of the results. The cumulative birth cohort incidence of diabetes was determined to have an increasing average annual trend of 2.5 per cent. Although the average birth cohort-specific age of onset was estimated to have decreased slightly over the years of observation, the trend could be a result of random variation.

Adolescent↗
PubMed1997

Cerebrovascular disease mortality in Spain, 1955-1992: an age-period-cohort analysis.

The purpose of this study was to assess the contributions of period and birth cohort effects to changes in cerebrovascular disease (CVD) mortality in Spain over the period 1955-1992. Poisson regression models were fitted to age-and sex-specific CVD mortality rates obtained from National Vital Statistics. In the period 1955-1975, CVD mortality remained stable. In the period 1975-1992, CVD mortality declined by 54% (rate ratio, RR: 0.46; 95% confidence interval, CI: 0.43-0.49) in males and 62% (RR: 0.38; 95% CI: 0.34-0.42) in females. The cohort effect was very small up to the generation born in 1905, moving clearly downward thereafter. CVD mortality for subjects born in the period 1945-1949 was lower than for those born in the period 1905-1909 by 68% (RR: 0.32; 95% CI:0.16-0.63) in males and 82% (RR: 0.18; 95% CI: 0.07-0.45) in females. Among the possible partial explanations for these effects are the decline in ischemic heart disease and rheumatic fever mortality, the drop in salt and alcohol intake, the reduction in smoking among males and blood pressure among females, and the widespread use of antihypertensive treatments in Spain over the last 20 years.

Adult↗
PubMed2000

Trends in the prevalence of social phobia in the United States: a synthetic cohort analysis of changes over four decades.

Previous analysis of data from the U.S. National Comorbidity Survey (NCS) [24] suggested that the lifetime prevalence of social phobia in the community has increased significantly in recent cohorts. Furthermore, a latent class analysis of NCS data [21] revealed two primary classes of persons with social phobia: those with exclusive speaking fears and those with one or more other social-evaluative fears. Social phobia in the other social fear group is more persistent, more impairing, and more highly co-morbid with other DSM-III-R disorders. The current report presents data on whether the cohort effect is a general aspect of social phobia or is specific to one of the NCS social phobia subtypes, and whether the cohort effect varies as a function of socio-demographic characteristics. Data were drawn from the NCS. Social phobia was assessed with a revised version of the Composite International Diagnostic Interview. Retrospective age of onset reports were used to estimate Kaplan-Meier survival curves for first onset of social phobia in each cohort represented in the survey. Comparison of these curves allowed us to make synthetic estimates based on retrospective reports of intercohort trends in lifetime prevalence. The lifetime prevalence of social phobia appears to have increased in recent cohorts. However, this increase does not exist among social phobics with exclusive fears of speaking. The increase is most pronounced among white, educated, and married persons, and it is not explained by increased co-morbidity with other mental disorders. The fact that the cohort effect is more pronounced for social phobia with one or more non-speaking fears is important in that this is generally a more severe form of the disorder with an earlier age of onset than social phobia with pure speaking fears. The fact that the cohort effect is most pronounced among people with social and economic advantage (i.e., white, married, well-educated) is intriguing and raises questions about the etiologic process that warrant further study in future research.

Adolescent↗
PubMed1996

Age-period-cohort analysis of suicide mortality rates in Spain, 1959-1991.

BACKGROUND: Although there is evidence that suicide rates may be increasing in Spain, formal epidemiological studies have been limited to specific cities or counties. The objective of this study was to investigate nationwide trends in suicide mortality from 1959 to 1991 in Spain, with emphasis on age, period, and cohort effects. METHODS: Age- and sex-specific suicide mortality rates from 1959 until 1991 were obtained from official vital statistics tables from the Instituto Nacional de Estadística, the official registry of vital statistics in Spain. Poisson regression and graphical methods were used to model and estimate age, period and cohort effects. RESULTS: Suicide mortality rates increased with age, with a proportional increment for each decade of life of 45% (95% confidence interval: 45-46%). In both males and females, age-adjusted suicide mortality rates decreased from 1959 until the late 1970s and early 1980s. In 1982, trends started to increase, returning to the levels of 1959 in less than 6 years. Cohort effects were small for cohorts born prior to 1940. For cohorts born after 1950, suicide rates increased markedly. CONCLUSIONS: The increase in suicide mortality in younger cohorts and the high rates of suicide in the elderly demand further investigation to establish causal mechanisms and preventive strategies.

Adolescent↗
PubMed1987

Birth cohort analysis of changing suicide risk by sex and age in Sweden 1952 to 1981.

The study aims at exploring the sex and age shift in suicide in Sweden. Data from the Causes of Death Register comprising suicides occurring in 1952 to 1981 among persons born in 1877 to 1966 were included. Analysis of linear regression of cumulative suicide incidence in successive birth cohorts yielded a shift toward younger ages and a general increase in female suicide risk. The statistical suicide risk in the 20 to 24 male age group has increased 3.6 times. The male to female suicide risk sex ratio has decreased for those older than 45, while it has increased among young adults. There is an urgent need of explanatory studies.

Adolescent↗
PubMed2003

The Maine-Seattle back questionnaire: a 12-item disability questionnaire for evaluating patients with lumbar sciatica or stenosis: results of a derivation and validation cohort analysis.

STUDY DESIGN: Analysis of health-related quality of life data obtained from a prospective cohort study of patients with sciatica due to an intervertebral disc herniation or lumbar spinal stenosis. OBJECTIVE: To derive and validate a shortened version of a previously validated 23-item modification of the Roland-Morris Disability Questionnaire. SUMMARY OF BACKGROUND DATA: For patients with low back pain, improving health-related quality of life is often the main goal of therapy. The Roland-Morris Disability Questionnaire is one of the best validated and most frequently used back-specific functional status measures. A shortened version may permit more widespread use in clinical and research settings. METHODS: Data from 507 patients with sciatica enrolled in the Maine Lumbar Spine Study were used to derive a shortened version of a 23-item modification of the original Roland-Morris Disability Questionnaire using qualitative and cluster analysis techniques. The internal consistency, construct validity, reproducibility, and responsiveness in detecting change over a 3-month period for a new 12-item scale was compared to the original 23-item scale. The 12-item scale was then validated in an independent cohort of 148 patients with lumbar spinal stenosis. RESULTS: Internal consistency was very good but modestly lower for the 12-item instrument compared to the 23-item original scale. Reproducibility over a 3-month interval was good and did not differ between the 12-item and original scale. Findings from the validation cohort were similar or better than the derivation cohort. A high degree of construct validity with patient-reported symptoms was demonstrated for the 12-item and original scales. The responsiveness and interpretability of the 12-item scale over 3 months was excellent and comparable to the original scale. Responsiveness assessed in patients with lumbar spinal stenosis in the independent validation cohort showed consistent findings compared to patients with a disc herniation in the derivation cohort. CONCLUSIONS: This short, simple, self-administered 12-item back-specific functional status questionnaire performed extremely well in comparison with the original 23-item scale. If validated in additional study populations, this new questionnaire may be useful in the clinical setting as a way for providers to prospectively compare their outcomes of care to other patient populations, and to study treatment effectiveness.

Adult↗
PubMed2004

Temporal trends of dengue fever/dengue hemorrhagic fever in Bangkok, Thailand from 1981 to 2000: an age-period-cohort analysis.

The aim of this study was to examine the effects of age, time period, and birth cohorts with dengue fever/dengue hemorrhagic fever (DF/DHF) in Bangkok, Thailand over the period 1981-2000. The age group at greatest risk for DF/DHF was 5-9 years old. The period effect shows a remittent pattern, with significant increases in 1986-1990 and 1996-2000. The birth cohort group showed a significant decreasing trend from the 1961-1965 group to the 1991-1995 group (R2 = 0.7620) with a decreasing rate of 0.1. We concluded that the temporal trend of DF/DHF is decreasing; especially for DHF.

Adolescent↗
PubMed1996

The effect of acute renal failure on mortality. A cohort analysis.

OBJECTIVE: To determine if the high mortality in acute renal failure is explained by underlying illnesses (comorbidity). DESIGN: Cohort analytic study. SETTING: An 826-bed general hospital providing primary, secondary, and tertiary care. PATIENTS: From 16,248 inpatients undergoing radiocontrast procedures between 1987 and 1989, we identified 183 index subjects who developed contrast media-associated renal failure (defined as an increase in serum creatinine level of at least 25%, to at least 177 micromol/L [2 mg/dL], within 2 days of receiving contrast material) and 174 paired subjects, matched for age and baseline serum creatinine level, who underwent similar contrast procedures without developing renal failure. MAIN OUTCOME MEASURE: Death during hospitalization. RESULTS: The mortality rate in subjects without renal failure was 7%, compared with 34% in the corresponding index subjects with renal failure (odds ratio, 6.5; P<.001). After adjusting for differences in comorbidity, renal failure was associated with an odds ratio of dying of 5.5. Subjects who died after developing renal failure had complicated clinical courses characterized by sepsis, bleeding, delirium, and respiratory failure; most of these complications developed after the onset of renal failure. Deaths from renal causes were rare. CONCLUSIONS: The high mortality rate in acute renal failure is not explained by the underlying conditions alone. Renal failure appears to increase the risk of developing severe nonrenal complications that lead to death and should not be regarded as a treatable complication of serious illness.

APACHE↗
PubMed1990

A cohort analysis of breast cancer, uterine corpus cancer, and childbearing pattern in Norwegian women.

STUDY OBJECTIVE: The aim was to study the influence of childbearing pattern on the incidence of breast cancer and uterine corpus cancer. DESIGN: This was an ecological study of birth cohorts of women. SETTING: The study was population based, involving the whole of Norway. PARTICIPANTS: The participants were Norwegian women born between 1890 and 1944. MEASUREMENTS AND MAIN RESULTS: Age specific fertility rates and age specific incidence rates for different birth cohorts were analysed by an age-cohort-period model where quantitative indices of the childbearing pattern substituted the cohort component. The 1890-94 birth cohort had the most favourable childbearing pattern with regard to the risk of breast cancer as well as uterine corpus cancer. The least favourable pattern was in the 1910-14 cohort for breast cancer and the 1940-44 cohort for uterine corpus cancer. In the analysis it is estimated that about 15% of the increase in incidence of breast cancer from 1955 to 1984 may be attributed to changes in the childbearing pattern of the cohorts under study. For cancer of the uterine corpus the corresponding fraction is about 27%. CONCLUSIONS: The study reveals that changes in childbearing pattern may explain a certain fraction of the observed increase in breast and uterine corpus cancer in Norway in the last 30 years, but the largest fraction must be accounted for by other factors.

Adolescent↗
PubMed2001

A birth cohort analysis of smoking by adults in Great Britain 1974-1998.

BACKGROUND: The aim of the study was to determine for Great Britain the percentage of current smokers and ever smokers by age in successive birth cohorts and the percentage of ever smokers who continue, by analysis of data from serial cross-sectional surveys of smoking status (General Household Survey). METHOD: A series of 5 year birth cohorts were followed through data from the 13 national surveys conducted at biennial intervals between 1974 and 1998. RESULTS AND CONCLUSION: In all birth cohorts, male and female, after age 25 years the percentage of current smokers falls with age. In the earliest birth cohort for males (1897-1901) about 85 per cent were ever smokers (i.e. had smoked at some time). After the 1922-1926 cohort this started to fall, to reach the level of about 50 per cent in the 1962-1966 cohort. In females only 25 per cent of the earliest cohort ever smoked but this rose, reaching about 65 per cent in the 1922-1926 cohort before falling back to about 50 per cent in the 1962-1966 cohort. The age at which smokers quit appears to be falling in successive cohorts. Once they have started quitting the rate at which smokers do so is very similar in all cohorts, with about 1 per cent of ever smokers quitting each year. If these trends are continued the UK smoking prevalence targets will not be met.

Adolescent↗
PubMed2004

Time trends of female lung cancer in Hong Kong: Age, period and birth cohort analysis.

The study was conducted to estimate the effects of age, year of diagnosis (period) and year of birth (cohort) on the time trend of female lung cancer incidence between 1976 and 2000 in Hong Kong. Data were obtained from a population-based cancer registry and the Census and Statistics Department. Using the Hong Kong general population of 1990 as the reference, age-adjusted incidence rates were computed by using direct standardization. We also analyzed secular trends in 2 consecutive periods, 1976-1990 and 1991-2000, using a Poisson regression model to estimate the annual percentage change in incidence rate. Age, period and cohort effects were assessed employing the method proposed by Clayton and Schifflers with 3 Poisson regression models fitted separately for age alone, age and period, and age and cohort. The age-adjusted incidence rate increased steadily up to 1990, when a peak of 40.1 per 100,000 was reached. Thereafter, a downward trend was observed. The overall annual increase was 4.2% during the period 1976-1990 with the fastest increase observed in women aged 80-84 years. An overall decrease of 2.3% was seen in the period 1991-2000, with the greatest reduction occurring in the 35-39 age group. After the adjustment for age, significant period and cohort effects on the time trend of incidence were observed. The age-cohort model provided a better description of the data than the age-period model. The risk of successive 5-year birth cohorts increased from 1896 to 1925 and then decreased. The time trend of lung cancer incidence of Hong Kong female in 1976-2000 had a marked birth cohort effect. Our results imply that major sources of exposure, which carry an increased risk of lung cancer for Hong Kong women, have been becoming less common in recent decades. Domestic air pollution, poor nutrition and tobacco smoking might have played important roles in the change of risks in successive generations and provide guidance for future interventions.

Adult↗
PubMed2003

High coronary heart disease rates among Dutch women of the baby boom, born 1945-1959: age-cohort analysis and projection.

BACKGROUND: After a steep decline in older generations, coronary heart disease mortality is stagnating in female cohorts born after the Second World War. We analysed past trends and predicted future health care needs for coronary heart disease in the Dutch population. METHODS: A loglinear age-cohort model relates numbers of deaths and hospital admissions for coronary heart disease to sex, age, birth cohort and population size, and projects age-cohort changes over the future population. Population size, population forecasts and coronary heart disease mortality (period 1970-1999) are from vital statistics. Numbers of hospitalised acute coronary events are from the nationwide hospital register (period 1980-1999). RESULTS: Among men, the rate ratios of deaths and hospital admissions were, respectively, 0.21 (death) and 0.78 (survivors at discharge) in the cohorts born in the period 1948-1962 compared to the period 1918-1922. Among women, the same rate ratios were 0.41 and 1.89. The projection model predicts 22% less deaths from coronary heart disease and 22% more survivors of an infarction in 2015, among men. Among women, there will be 5% less deaths and 70% more survivors of an infarction, most of these being middle age members of the baby boom cohorts. CONCLUSIONS: Stagnating all-cause mortality is correlated with an upward trend in coronary heart disease risk in the female baby boomers. Heart health care needs among middle-aged women will increase sharply. These changes are correlated to high lung cancer mortality and high smoking rates in these cohorts.

Adult↗
PubMed2007

Melanoma incidence in central Italy will go on increasing also in the near future: a registry-based, age-period-cohort analysis.

The aim of the study was to evaluate malignant melanoma incident trends in central Italy by means of an age-period-cohort approach. A total of 1977 malignant melanoma (15-84 years) incidents in the area of the Tuscany Cancer Registry between 1987 and 2001 were analysed. Poisson regression has been used to estimate age, cohort and period effect. A nonlinear regression model was used to estimate the expected number of new cases in the period 2002-2006. Incidence rates increased in all age, period and cohort groups. The model that best fitted the data included age and 'drift'. The linear effect ('drift') showed, in each age group, an increase of the risk of malignant melanoma diagnosis of about 36.6% every 5 years of period or cohort. For the period 2002-2006, 1112 new cases were predicted with a standardized rate (age 15-84 years) of 19.2x100.000. In the Tuscany Cancer Registry area, no clues for malignant melanoma incidence rates levelling off were documented. Growing rates and number of malignant melanoma are expected in the near future.

Adolescent↗
PubMed1999

[Birth cohort analysis of obesity in an occupational setting].

PURPOSE: The purpose of this study was to analyze the transition of body mass index (BMI) by birth cohort and to determine the relationship between BMI and high blood pressure, for the health management of workers in an industry. SUBJECTS AND METHODS: The eligible study subjects were 3,043 male workers at printing and papermaking plants who were 20 to 49 years of age in 1986 and whose annual health checkup information was available for both 1991 and 1996. First, we analyzed the transition of BMI by 5-year birth cohort. Second, we analyzed the relationship between BMI and high blood pressure (systolic blood pressure > = 140 mmHg or diastolic blood pressure > = 90 mmHg) using multiple logistic regression models. In this analysis, we excluded 596 subjects who were diagnosed as having high blood pressure in 1986 and 17 subjects whose alcohol drinking habits were unknown. Consequently, we had 2,430 study subjects. RESULTS: (1) All the birth cohorts showed that the proportion of obese subjects (BMI > = 26.4) became higher as age advanced. The proportion was higher for younger cohort. (2) By multiple logistic regression models, age at the beginning of the study, BMI, change of BMI in 5 or 10 years, and alcohol drinking habits were related to the risk of having high blood pressure. CONCLUSION: In the health management of workers, it is necessary to evaluate the risk by birth cohort. Also, we consider that we need to initiate obesity counseling before the workers become 30 years of age.

Adult↗